Pulsed liquid wire electrohydraulic system

ABSTRACT

An electrohydraulic container forming device wherein a thin stream of conductive fluid constitutes a bridge between one electrode and the other of the shock producing electrodes. The conductive liquid is pressurized to a higher value than the internal pressure of the container. In operation the conductive liquid is emitted under pressure from one electrode by a timing circuit driving a shear type solenoid valve. A second timing circuit synchronizes the electrical discharge with the establishment of a preferentially conductive bridge across the electrode gap. A sharp jet pulse is given off from the arc thus established and this develops pressure inside the rubber diaphragm to press it against the container which is then pressed into the interstices of the die to give a fully stylized container.

United States Patent Norin et a1.

[54] PULSED LIQUID WIRE ELECTROHYDRAULIC SYSTEM [73] Assignee: Continental Can Company,

York, NY. I 22 Filed: Aug. 17,1910 21 App1.No.: 64,394

Inc., New

Related US. Application Data [62] Division of Ser. No. 762,457,Sept. 25, 1968, Pat. No.

[1 1 3,668,365 [451 June6, 1972 Jost ..219/119 3,253,442 5/1966 Grove et a1. ..72/56 Primary Examiner-R. F. Staubly Assistant Examiner-Gale R. Peterson [57] ABSTRACT liquid is emitted under pressure from one electrode by a timing circuit driving a shear type solenoid valve. A second timing l%z circuit synchronizes the electrical discharge with the establish- I'lt J ment of a preferentially conductive across the elec [58] FreldofSearch ..219/l19,120, 145, 1493712505365; "ode A Sharp jet pulse is given off fmm the are thus established and this develops pressure inside the rubber diaphragm to press it against the container which is then [56] References cued pressed into the interstices of the die to give a fully stylized UNITED STATES PATENTS commer- 2,281,335 4/1942 Somes ..219/120 4 Claims, 9 Drawing Figures I n POWER SUPPLY 8 TIMING CKT.

. iii- HIGH VOLTAGE POWER SUPPLY PWR. suPPLY PATENTEDJUH SL972 3.668.365

sum 20F 4 POWER SUPPLY 8 TIMING CKT.

HYDRAULIC CKT. ELECTRICAL CKI FOR CONDUCTIVE FOR HYD. CKT. 8|

FLUID TIMING CKT.

HIGH VOLTAGE TRlGGERaTlMlNG POWER CKT. FOR H.V. SUPPLY PWR. SUPPLY IN VENTORS ROBERT W. NOR/ N DONALD .1 ROTH BY 4 ATT 'Y.

PATENTEDJUN 5 m2 SHEET 3 BF 4 IN VE N TORS ROBERT W NOR/N ONALD J. ROTH BY 4 ATT'Y.

PATENTEDJua 6 m2 SHEET l 0F 4 INVENTORS ROBERT W. NOR/N DONALD J. ROTH BY W ATT'Y 1 PULSED LIQUID WIRE ELECTROHYDRAULIC SYSTEM RELATED APPLICATIONS This patent application is a divisional application of copendingpatent application Ser. No. 762,457 filed Sept. 25, 1968 and now U.S. Pat. No. 3,566,648.

Our invention relates to a conductive bridge forming device and' particularly to an electrohydraulic forming device wherein the bridge is formed by an intermittent supply of conductive liquid under pressure.

The use of electric arcs for metal forming or working processes has been known for some years, however, the establishment of a preferential conductive pathway is of relatively recent origin and has been essentially limited to the use of bridge wires. In the process of forming an electrohydraulic arc the bridgewire is destroyed and before another arc can be established, a new bridge wire must be placed between the electrodes. v

It is an object of our invention to provide an intermittent preferential conductive current path.

It is another object of our invention to provide a means for controlling the application of the con uctive fluid to the electrode gap.

It is an object of our invention to provide an intermittent conductive bridge between electrodes.

It is another object of our invention to provide a dispersing electrode to prevent high conductivity in the surrounding gap area.

Another object is to provide a preferential conductive pathway which may be renewed without disassembly of the apparatus.

Another object of this invention is to provide an electrohydraulic forming operation of high and repeatable efficiency.

In brief, our invention is to a preferential conductive fluid path for spark discharge between cathode and anode immersed in a non-conductive or less conductive liquid than the conductive liquid for the preferential path. The liquid flows from one electrode through a small intervening space to another electrode. A high voltage, high amperage power supply is connected across these electrodes so as to fire synchronously withthe pulses of the conductive liquid.

These and other objects will become apparent from the following description and drawings in which:

FIG. 1 is a representation of the electrohydraulic stylizing machine showing the machine partly in section and partly broken away.

FIG. 2 shows the relationship of the electrical circuits, the pressure chamber and the die. a

FIG. 3 shows the lower electrode in three views, A, B and C.

FIG. 4 shows a schematic of the machine hydraulic circuitry and the hydraulic conductive fluid circuit.

FIG. 5 shows a timing circuit for the conductive fluid pulse.

FIG. 6 shows a DC. power supply and initiation circuit for the circuits of FIGS. 5 and 7.

FIG. 7 shows an electrical trigger and timing circuit for firing of the high voltage power supply.

FIG. 1 shows the electrohydraulic chamber 1 of this invention placed in a forming apparatus. This invention is adapted to be used as the electrohydraulic forming apparatus in any one of a number of machines for forming tubular workpieces. The electrohydraulic bag or boot 4 of FIG. 2 is shown surrounded by a stylized die 2. The side of a tubular container 3 is located between the chamber wall 4 and the inside die wall 5. The other wall of the chamber is made of rubber or some other durable elastomeric material to form a bag. Arelatively incompressible, non-conductive liquid such as-water, which transmits pressure is'used to fill the chamber. As shown, two electrodes are mounted within the chamber, one electrode 7 is suspended from the top into the chamber and the other 8 is mounted on pillars 9 and extends upward from the bottom of the chamber. The lower electrode 8 is connected to one side 10 of the high voltage powersupply. Another electrode 7 is connected to the other side 11 of the high voltage power supply 12 and the entire chamber 4 fits inside the die 2 as a sort of plug device. The upper electrode 7 is separated from metal plug element 13 by an electrical insulator 14. Passages 15 are provided through the plug device for the water or other media to be conducted into and out of the chamber.

The electrodes may be in any configuration or position relative to each other so long as a preferential conductive bridge is established between them in a manner similar to that indicated below.

In operation the jet which streams out of the upper'electrode 7 and passes down into the lower electrode 8 forms a bridge. This jet is powered from the hydraulic circuit 16 for conductive fluid and is snychronized with the current discharge from the high voltage power supply 12. It is not necessary for the bridge to be completely formed as long as a preferential path is established for the flow of electricity. The conductive bridge between the electrodes must be formed to the extent that a preferential pathway for electricity is established before the high voltage power supply 12 is connected across the bridge. The timing for the hydraulic circuit 16 as shown in (FIG. 4) is controlled through the electrical circuitry generally indicated 17 as shown in (FIG. 5) and 19 as shown in (FIG. 6) while the synchronous timing is controlled through the circuit'generally indicated 18 as shown in (FIG. 7).

The structure of the lower electrode 8 which serves a dual purpose is shown clearly in FIG. 3A, B and C. This electrode is generally the cathode because the anode is placed in the upper position to be more accessible for replacement. When the electricity arcs between the electrodes'the anode erodes more rapidly than does the cathode.

The lower electrode 8 serves as a dispersing electrode with channels 20, 21 located so that the thin stream of conducting liquid which is jetted from the channel in the upper electrode toward the lower electrode is passed through channel 20 in the lower electrode and deflected toward the side through channel 21, in this way the liquid bridge is the only concentration of conductive liquid in the region between the electrodes. The electric current passes from one electrode through'the conductive bridge to the other electrode and the pressure waves generated by successive arcings have similar shapes and pressures because they are generated under similar conditions.

The hydraulic circuit 16 is controlled by an electrical circuit having a switch (not shown) to turn on the pumps in the hydraulic circuit. When the hydraulic pump 19 (FIG. 4) commences operation the pressure throughout the circuit builds up. Electric switch and solenoid operation may be controlled by a series of cams mounted on a rotating shaft or alternatively may be controlled by an electrical time delay circuit. In any case the control relay 20' shown in FIG. 6 operates when the cam 21 shown in FIG. 6 closes the normally open conductive fluid bridge initiator switch 22 which activates contacts 24 of the conductive fluid timing circuit shown in FIG. 5 and the contacts 25 of the high voltage power supply time delay circuit shown in FIG. 7 thus allowing these timing circuits to begin operation.

The circuits connected to these relay contacts provide a time delay for establishing the conductive bridge and a time delay for switching the power supply to the electrodes to form an are through the conductive bridge. The time delay circuits may be varied as pointed out later in this specification to allow the electric current and the conductive bridge to be applied across the electrode gap in a predetermined time relationship.

The hydraulic circuit is shown schematically in FIG. 4. There are basically three systems involved in the hydraulic circuit. One is the oil system used for applying pressure to the conductive fluid system, another is the conductive fluid circuit in which the conductive fluid is finally jetted through an electrode on an intermittent basis to provide a preferential power supply discharge across the electrodes and the third is the pressure transmission and flushing system.

in place.

To start the stylizing machine hydraulic .pump'l9, water pump 26Iand'vacuum' pump 27. are all turned on. When the hydraulic pump .19 begins operation a high pressure is built-up in its exit conduit 28. The pressure iscontrolled by valve 29 and in practice ranges about 550 p.s.i. or higher. Since the I master valve 30 is in itsnormal position no oil pressure is passed through it.. .Thus, accumulator 31 which has a precharge of fairly high pressure of air in it is now compressed. This pressureis passed to the oil side of the intensifier 32.

Each accumulator has a diaphragm between its fluids to avoid aeration of dissimilar fluids.

H Starting from the situation in which theplug or stylizer has just completely stylized the can i.e., the can has been pre-pressurized and coined. The can is now taken out of the-machine and. the following operationtakes place. 7

' First, all solenoids except solenoid 33 are de-energized. Solenoid No. 33 is energized and :valve 34 is opened-.'In' this situation the bag 4 or rubber diaphragm surrounding plug 13 I has suction applied through conduit 35 by the vacuum, pump 27. While .thebag is beingevacuated by the vacuumpump a and other pressure regulator To complete this cycle the solenoid 36 is de-energized as arethe other valves and the chamber formedby the bag is cutoff from all other pressures.

Solenoid 38 is now energized and valve 39 of the master valve 30 is open in thecircuit. All other valves arede-energized. The 550 lbs. pressure in accumulator. 3l is nowconnected to the oil chamber 40 of intensifier 32. A somewhat ,higher pressure of about 600 lbs. will come out of intensifier 32. and pre-pressure the container at about600. p.s.i. At the same time-the 550'lbs. pressure passes through conduit 41 to tandem cylinder intensifier 42 and generates a conductive solution pressure of approximately L000 p.s.i. in the 40-foot insulation hose 43.This hose is in a coiled form 44 to act as an impedance to the passage .of electric current-through it. When the pump pressure of about 600 p.s.i. .is applied to the chamber any air which may be entrapped between the bag and the tubular workpiece is totally eliminated and the machine is in condition so that when the subsequent very high pressure is put on the inside of the chamber the tubular side of the can is pressed into the die to rough form the can into the general configuration of the die. Any air which may be entrapped between the can and the die is minimized. Concurrently, the oil side of accumulator 45 is connected to the oil reservoir 46 through the master valve configuration 39 so that the conductive solution 47 under pressure flows into the accumulator 45 to replenish the supply. The conductive solution is under a pressure of approximately 60 p.s.i. In the pre-pressuring step the can is loaded with a pre-pressure of less than the ultimate internal pressure but high enough to rough form the can into the general contour of the die.

After the can has been pre-pressu'red a quite high pressure is applied to the inside of the can so that it is forced against the die to form an almost exact replica of the die i.e. the can is coined. Tojbring about the high pressure a preferential-conductive pathway of conductive liquid is formed between the electrodes 7 and 8- and a quick surge of electric current is passed through the preferential conductive pathway to form an arc andgenerate a pressure wave. Contact relays 20' of FIGS. 6 is activated to effect closing of their respective contacts 24 and 25 when switch 22 of FIG. 6 is closed by the revolving cam2l. Time delay circuits l9 and 17 (FIGS. and 7) are regulated in such a manner as to allow solenoid 48 to open the wire jet initiator valve 49 before electrical power or potential is applied across the electrodes 7 and 8. In this way,

the preferential path bridge is established before electrical potential is applied across the electrodes.

i The volume of the conductiveliquid in the bridgeis small "and the resilience of the conduit and hose is'sufficient to provide an=accumulator-eifect of this magnitude. If higher volumes of conductive liquid are needed a hydraulic accumulator may be installed.

Contacts 25 of the time delay trigger circuit (FIG. 7) closes at thesame time as contacts 24 of the conductive fluid (FIG.

' 5) timing circuit as pointed out'above. However, these circuits do=not actuate'their operators at the same time because the .variables of the time'delay trigger circuits are adjusted so that the timedelay trigger circuit 19' of the power supplyfires a thyratron and ignitron (not shown) in electrical circuit at a predetermined time interval after the electrode hydraulic v liquid wire jet initiator valve 49 has opened to cause the .preferential'pathway to be formed. In this connection it is noted that the variable resistor 50 andcapacitor' Sl'of FIG. 5

may be-varied to whatever value is necessary to cause their respective circuits tooperate at a predetermined time after the initial closing of the contacts 24 in the circuit. Similarly,

the' time'delay trigger circuit (FIG. 7) has a variable'resistor '52 and capacitor 53 which may be varied to cause this circuit 'to operate a predetermined time after solenoid 48 has opened the wire jetinitiator valve 49.

The operation of the relaxation circuit of FIG. 5 is as follows. Once the relay contacts 24 close in the timing circuit, transistor (2N3055)'23 becomes conductive and allows current to flow through solenoid 48 to open valve'49 (FIG. 4) because of the voltage increase across silicon rectifier 55 -(SCR-C6B). Once voltage is built-up across the capacitor 5 I (IOmfd), transistor 54 (2N489) becomes conductive causing silicon rectifier 55 (SCR-C6B) to become conductive and reduce thevoltage across it. The net'e ffect of this relaxation circuitis togive a timed pulse to the solenoid 48 and cause solenoid valve49to be open only during such period of time as is required to bring about a preferential pathway for electric currentbetween the electrodes.

The operation of the relaxation circuit of FIG. 7 is essentially the same as that of 'FlG. 5, with the exception that the outputpulse generated from the trigger circuit for the power supply is delayed until such time that the preferential conduc tive bridge is established across the electrode gap.

The powersupply has now discharged across the electrodes and has formed a pressure wave having a steep front which pressed against the baglside and coined the pre-pressurized tubular material into the surrounding die.

' 56. The change of volume of the space 56 is less than the volume of the conduit 35 so that the debris and other impurities are drawn up into the conduit 35 but not into space 56. The volume of the space 56 is larger than the amount of water used to pre-pressure the can because intensifier 32 pre-pressures the can to give it its initial rough forming. Dies vary in contour and the amount of water necessary to give a rough forming varies depending on the contour of the die. Thus different intensifiers may be used with difierent dies depending on the die contour to give a different intensifierspace 56. Oil

and water. may leak past O-rings 57 as the piston 55 works.

I drain 58. The bag size, however, is somewhat shrunk due to the forces now acting on it since the outside is connected to atmosphen'c pressure and the inside is under negative pressure through the lines 35, 59 and 60. Thus the bag is shrunk around its supporting framework.

After the shock wave has been formed, gas bubbles remain in the liquid and a certain amount of debris from the electrodes is carried into the chamber. If air bubbles are allowed to remain in the chamber they cause softening of the shock wave and the coining effect is small. The electrode debris, if

greater amount of water comes into the bag that is passed out of it, the bag will expand.

Since it is difficult to exactly balance the water coming in with the water going out, now valve 37 is closed and vacuum applied through valve 34 evacuates the bag again so that the bag is shrunk onto the framework 9 (FIG. 2). The speed of response of the system is heightened by the reservoir 61. Reservoir 61 is under a base pressure of p.s.i. of air from the air pump 62. Water pump 26 delivers a higher pressure of about 60 p.s.i. used for flushing the chamber. Thus reservoir 61 and its air are usually under a pressure between 20 and 60 p.s.i. depending on the degree of exhaustion of water from the reservoir.

At the same time or immediately after the bag is shrunk onto the framework, solenoid 3 moves the master valve 30 to configuration 64. Intermediate pressure of about 550 p.s.i. is thus applied to the oil side of intensifier 32 and 550 p.s.i. is applied to the larger cylinder of intensifier 42 for replenishment.

When configuration 64 of the master valve 30 is actuated, 550 p.s.i. is applied tothe oil side of the accumulator 31. The oil in the accumulator is replenished. This in turn will apply 550 p.s.i. to the conductive solution 47 in top of the accumulator 45 and this brine will apply about 550 p.s.i. to the smaller cylinder of the tandem cylinder 42 to replenish the brine in the tandem cylinder intensifier.

Finally to complete the cycle the master valve 34 is returned to normal by de-energization of solenoid 63, the dies are withdrawn from'around the stylized canand the stylized can drops off of the shrunk bag.

The cycle is now ready to be repeated again.

The can stylizing machine and its electrohydraulic chamber may operateto stylize many cans per minute. Thus the cycle set forth above is repeated many times per minute. Any device may be used to make and break the conductive fluid bridge initiator switch 22 (FIG. 6) to start and stop each cycle. For example, an off center cam may be synchronized with the stylizing machines operation to open and close the circuits and to move the valves. The valves may be spring loaded to return the valves to their original position afterthe can has passed. The pumps run continuously. To avoid burning out of the vacuum pump, valve 65-opens when valve 34 closes and visa versa. In this way a small amount of material is passed into the vacuum pump at all times during operation of the machine.v

Tanks 66 and 67 are air collection tanks. As pointed out above, air in the water lessens the effectiveness of this machine particularly and slows the speed of response of any hydraulic machine. Tanks 66 and 67 are mounted at the top of the machine in such a way that air included in the water supplied to the system finds its way into the top of these tanks and is bled from time to time. To summarize the system operation:

1. Chamber evacuation step SV 63, 38, 48, 36 and 68 de-energized SV 33 energized 2. F lll chamber cycle (pick up new can over bag, dies close around bag and can) SV63, 38, 48, 33 and 68 de-energized SV36 energized 3. CutolT SV36 de-energized 4. Bulge or pre-pressure can SV38 energized 5. Pulse for preferential conductive electric discharge Electrical timing circuits commence v SV48 energizes momentarily to form a preferential conductive pathway path and power supply Highvoltage circuit fires to supply sharp electric discharge and coin can 6. Evacuate bag SV38 de-energized, master valve back to normal 7. Flush-out explosion chamber SV33 and 36 energized 8. Vacuum applied to evacuate chamber and to shrink bag to framework SV36 de-energized SV33, 63 energized 9. System recharged by step above.

SV 63 deenergized 10. Cycle completed.

Master valve to normal, dies withdrawn, stylized can dropped off.

' it is apparent from the above that the chamber is pre-pressurized to rough form the can before a conductive solution is fed through electrode 7 (FIG. 2) to form a preferential bridge circuit. Fresh water is put under pressure through intensifier 32, and sufficient pressure is applied to the side of the can wall to rough form it into the surrounding die 2.

Afirst advantage is that by pulsing the conductive solution across the electrodes there is a saving of conductive solution.

A further advantage is that the establishment of a preferential path causes the arc to take place at the same place and with the same strength and pattern each time.

Another advantage is that the use of a dispersing electrode prevents accumulation of highly conductive materials throughout the gap area.

Another advantage is that many cans per minute may be turned out by this machine.

Another advantage is low consumption of salt.

A final advantage is higher energy conversion efficiency compared to conventional electrohydraulic arc discharge.

The foregoing is a descriptionof the illustrated embodiment of the invention and it is applicant's intention in the appended claimsto cover all forms which fall within the scope of the invention.

What is claimed is:

1. In an electrohydraulic forming device having a conductive fluid bridge circuit for the generation of an electric arc in a pressure transmitting medium of the class wherein a chamber contains a non-conducting fluid, a first electrode extending into said non-conductive fluid, a first channel means through said first electrode whereby a conductive fluid may be jetted through said channel means into saidnon-conductive fluid, the combination therewith of a dispersing electrode mounted in spaced opposition to said first electrode and having a first and a second end, and second channel means extending from said first end .of said dispersing electrode in a direction away from said first electrode part way to said second end of said dispersing electrode, a third channel means extending transverse to said second channel means through said dispersing electrode and connecting to said second channel means whereby conductive fluid which jets from said first channel means into said second channel means may then flow laterally through said third channel means to be dispersed away from said dispersing electrode into the non-conductive fluid in said chamber.

2. In an electrohydraulic container forming device as set forth in claim 1 in which said second channel means comprises,

a passageway extending from said first end of said dispersing electrode to a point about halfway along its length.

3. In an electrohydraulic container forming device as set forth in claim 2 in which said third channel means comprises:

a passageway having its exit orifices extending around the circumference of said dispersing electrode and its entrance way connected to said second channel passageway.

4. In a conductive fluid bridge circuit of the class wherein a non-conductive fluid is in a chamber and a first electrode having an axis extends into the non-conductive fluid, a first channel extends along said axis whereby a conductive fluid may be second channel whereby conductive fluid which jets from said first channel into said second channel may then flow laterally through said conduit means to be dispersed away from said second electrode into the non-conductive fluid in said chamber. 

1. In an electrohydraulic forming device having a conductive fluid bridge circuit for the generation of an electric arc in a pressure transmitting medium of the class wherein a chamber contains a non-conducting fluid, a first electrode extending into said non-conductive fluid, a first channel means through said first electrode whereby a conductive fluid may be jetted through said channel means into said non-conductive fluid, the combination therewith of a dispersing electrode mounted in spaced opposition to said first electrode and having a first and a second end, and second channel means extending from said first end of said dispersing electrode in a direction away from said first electrode part way to said second end of said dispersing electrode, a third channel means extending transverse to said second channel means through said dispersing electrode and connecting to said second channel means whereby conductive fluid which jets from said first channel means into said second channel means may then flow laterally through said third channel means to be dispersed away from said dispersing electrode into the nonconductive fluid in said chamber.
 2. In an electrohydraulic container forming device as set forth in claim 1 in which said second channel means comprises, a passageway extending from said first end of said dispersing electrode to a point about halfway along its length.
 3. In an electrohydraulic container forming device as set forth in claim 2 in which said third channel means comprises: a passageway having its exit orifices extending around the circumference of said dispersing electrode and its entrance way connected to said second channel passageway.
 4. In a conductive fluid bridge circuit of the class wherein a non-conductive fluid is in a chamber and a first electrode having an axis extends into the non-conductive fluid, a first channel extends along said axis whereby a conductive fluid may be jetted through said first channel and out of said first electrode and into said non-conductive fluid, the combination therewith of a second electrode mounted in spaced opposition to said first electrode and having an axis and a first and a second end, and a second channel extending from said first end of said electrode along said longitudinal axis part way to its second end, conduit means extending across said electrode from said second channel whereby conductive fluid which jets from said first channel into said second channel may then flow laterally through said conduit means to be dispersed away from said second electrode into the non-conductive fluid in said chamber. 